Hi
Thank you for reaching out to us. I'm so sorry you are facing issues!
I'm Maggie, an Independent Advisor from thr user community. I love helping other users in the Community by sharing my experience with Microsoft products.
Unfortunately that feature is not available today. It is not possible to bulk hide chats nor to bulk delete them.
I would recommend that you should send this feedback to Skype engineers :
https://skype.uservoice.com/forums/914527-welco...
You can add new ideas or vote in the existing one. Microsoft teams look at the requests in this forum and consider them while planning and developing new updates.
I understand it's probably not the answer you were looking for, but I hope you'll at least clarify it. If you have any further questions, I'm here to help.
Hope this helps!
I wish you a great day/night :)!
Maggie